The study carried out by former Tory party donor Lord Ashcroft found that Mr Cameron is less popular than his party for the first time.

The poll showed a “noticeable shift” towards dissatisfaction with the Prime Minister's performance, while the Tories lost ground on key issues like crime, immigration, welfare reform and the economy over the early months of this year.

Lord Ashcroft blamed the Tory setbacks on the party putting people off by “talking amongst ourselves” about peripheral issues like Europe and gay marriage rather than focusing on voters’ core priorities.

He issued a warning to the party's leadership that there was “no time to waste”, and said it was vital for Chancellor George Osborne's spending review later this month to show that Tories are doing what the public want from them.

Overall, 37 per cent of those questioned said they would vote Labour, 27 per cent Conservative, 15 per cent the UK Independence Party and 9 per cent Liberal Democrat, giving Ed Miliband’s party a comfortable 10-point advantage, though Lord Ashcroft noted that this was “not much of a score for an opposition party expecting to sweep to power in 23 months’ time”.

A majority still said they would prefer to have Mr Cameron than Mr Miliband in Downing Street, and the Prime Minister and Chancellor George Osborne retained their lead over Mr Miliband and Shadow Chancellor Ed Balls as the best team to manage the economy.

One bright light for Lib Dem leader Nick Clegg was that the Government's lead over Labour on the economy widened by several points if the Deputy Prime Minister was named in the question as one of a three-man team alongside Mr Cameron and Mr Osborne.

Perhaps the most striking finding in the poll was that 22 per cent of those questioned said they were more favourably disposed towards the Conservative Party as a whole than towards its leader, compared with 18 per cent saying the opposite - the first time this has happened in the series of Ashcroft surveys over the last few years.

Despite some grumbling from backbenchers, Mr Cameron has generally been viewed by Tories as an electoral asset because he has consistently outpolled the party on public popularity.

Writing on the ConservativeHome website, Lord Ashcroft said: “The Prime Minister's Europe speech (in January) was supposed to clear the decks and allow us to talk about the things we were elected to do.

“So much for all that. My poll shows the last six months to have been a missed opportunity to make progress on all the things that will determine who wins in 2015... This is the price we have paid for spending half a year talking amongst ourselves.”

For the Tories, the first half of the year was “a time of stagnation that we could hardly afford”, said the Tory peer, adding: “The spending review later this month makes it all the more necessary to show we are doing what people expect of us. There is no more time to waste.”

The poll found that only 28 per cent of voters see the Conservatives as “united”, against 48 per cent for Labour.

Some 38 per cent trusted Mr Cameron and Mr Osborne to manage the economy, compared with 33 per cent for Ed Miliband and Ed Balls.

But 40 per cent trusted Mr Cameron, Mr Osborne and Mr Clegg with the economy, against 26 per cent for the Labour team, suggesting that Lib Dem influence on the coalition's economic policy is welcomed by voters.

Of those questioned, 24 per cent said they were satisfied with the job Mr Cameron is doing as PM, and a further 33 per cent say they are dissatisfied but would prefer to have him in Downing Street than Mr Miliband.

Only 30 per cent would rather see the Labour leader in Number 10.

Some 40 per cent said they expect a Labour government after the next election, while 29 per cent forecast a Conservative government, 13 per cent another Conservative-Lib Dem coalition and 18 per cent a Labour-Lib Dem pact.

Some 2,060 adults were interviewed online and 1,007 by telephone between May 31 and June 2.